1. Field of the Invention
The present invention relates to an inkjet printing apparatus and a calibration method, specifically, an art to measure an image when the color and color density of an image printed with ink is measured and printing properties of the printing apparatus are calibrated on the basis of the measured result.
2. Description of the Related Art
When calibration is performed, a patch for measurement is first printed. A printing paper on which this patch was printed has relatively large difference in its moisture content between immediately after printing and after fixing a color, due to ink ejected onto the printing paper, so that much difference of color between them occurs. Therefore, in calibration, it is preferable that measurement is performed in a final state of the printing paper, that is, a state where the printing paper is dried and the color is stabilized. In doing so, since natural air drying takes much time, a forced drying mechanism, such as a mechanism to spray the printing paper with hot air, a radiation heating mechanism or a conduction heating mechanism, is often used.
However, if a printing paper is dried using such a forced drying mechanism, the printing paper has a high temperature immediately after drying treatment. Therefore, as this high temperature drops to a temperature of an ambient atmosphere and a moisture content of the printing paper changes to the equilibrium amount in the ambient atmosphere, a color (tone and density) of an image for measurement also changes. As a result, there is a problem that a measured value varies depending on a time when measurement is performed while the color is changing.
To deal with this problem, Japanese Patent Laid-Open No. H10-268589 (1998) describes that a waiting time is provided after a color material is fixed onto a printing paper by a fixing apparatus until measurement. This permits measuring a printed image whose color has been sufficiently stabilized.